This example visualizes the top 10 most populous countries as a bar chart, with a dropdown to switch between years of immigration data. The bars update based on the selected year, and tooltips show exact values. Built with React and D3 v5, it uses `scaleBand` for the x-axis, `scaleLinear` for the y-axis, and SVG `<rect>` elements for marks. Data comes from the United Nations World Population Prospects 2019, loaded via `csv` from a gist URL.